Subterranean drilling systems that employ downhole drilling motors are commonly used for drilling boreholes in the earth for oil and gas exploration. Subterranean drilling systems typically include a housing enclosing a downhole drilling motor operably connected to an output shaft. One or more thrust-bearing apparatuses may also be operably coupled to the downhole drilling motor for carrying thrust loads generated during drilling operations. A rotary drill bit may also be connected to the output shaft and be configured to engage a subterranean formation and drill a borehole. As the borehole is drilled with the rotary drill bit, pipe sections may be connected to the subterranean drilling system to form a drill string capable of progressively drilling the borehole to a greater size or depth within the earth.
Each bearing apparatus may include a stator that does not rotate and a rotor that is attached to the output shaft and rotates with the output shaft. The stator and rotor may each include a plurality of superhard bearing elements or inserts. Each superhard bearing element may be fabricated from a polycrystalline diamond compact (“PDC”) that provides a bearing surface that bears against other bearing surfaces during use.
In a conventional PDC bearing apparatus, a bearing assembly may include a support ring that includes recesses configured to accept the superhard bearing elements. The superhard bearing elements may be partially disposed in the recesses of the support ring and secured partially therein via brazing or other processes. However, heating and/or cooling from brazing and other processes may generate significant residual stresses in the superhard bearing elements. These residual stresses alone and/or in combination with operational loads may cause fracturing and/or weakening of the superhard bearing elements which may result in failure of bearing assemblies and/or bearing apparatuses.
Therefore, manufacturers and users of bearing apparatuses continue to seek improved bearing assembly and apparatus designs and manufacturing techniques.